These studies are designed to assess prospectively preferred methods of therapy and long term sequelae of bacterial meningitis in children in whom the etiologic diagnosis has been made rapidly and whose treatment has been provided according to specific protocols supervised by specialists in pediatric infectious diseases and neurology. New insights into the pathogenesis of Hemophilus influenzae meningitis will be sought. In particular, antigenic stimuli provided by H. influenzae disease will be quantitated and correlated with antibody responses in the same children in an attempt to gain information which may be important in the ultimate development and application of effective H. influenzae vaccines for the prevention of H. influenzae meningitis in infancy and childhood. Specific studies will be directed towards an evaluation of the interaction of Hemophilus influenzae, type b and its capsular polysaccharide (PRP) with antibody. An attempt will be made to determine the importance of cellular adherence in the response of children of various ages to H. influenzae infection. Investigation of the role of the normal anaerobic flora in the nasopharynx and gastrointestinal tract in the production of cross-reacting immunity of H. influenzae will be undertaken. Studies of secretion of antidiuretic hormone in children with meningitis will be conducted.